This invention is related to seals for ball valves or so called spherical plug valves which have the seal ring and the valve member constructed of metallic materials in order for the valve to withstand operation in a high temperature environment. This invention is related to ball valves which have seals formed of relatively thin deformable annular metallic members which will flex upon movement of the ball to maintain sealing engagement with the ball in all operating positions.
In the known prior art several patents are known which disclose ball valves having thin annular seal members disposed generally radially in the valve body around the flow passageways. These patents are Clade U.S. Pat. Nos. 2,890,856 and 2,942,840, R. P. Kulisek U.S. Pat. No. 3,056,576, and K. Kushida U.S. Pat. No. 3,841,347. These patents disclose seal rings made of a composite metallic and non-metallic material as well as seal rings of a solid metallic material. In these valves the seal rings are clamped in the valve body around the perimeter of the individual seal rings. One disadvantage of the peripherally mounted seal ring construction shown in these patents is that precise sizing of the parts and assembly of the valve is required to properly clamp the seal ring so the portions which support it in the valve body are not over-stressed, unduly deformed or otherwise damaged. The use of composite metallic and non-metallic seal rings in such valves is not acceptable for high temperature applications because the non-metallic material will decompose quickly at elevated temperatures. The patent of Kushida, U.S. Pat. No. 3,841,347, shows the use of several layers of metals to form a seal ring, however, this is also believed to be unacceptable for high temperature applications because of the inherent variation in thermal expansion characteristics of the different materials.